1. Field of the Invention
This invention relates to an immersion-processing method and apparatus for plating or surface-treating metallic products.
2. Description of the Related Art
In the conventional production of slide fasteners, various plating, such as copper-plating, nickel-plating, zinc-plating or brass-plating, have been made on slide fastener parts of zinc alloy to meet various demands. In each conventional plating processes, as disclosed in, for example, Japanese Patent Laid-Open Publication No. Sho 55-14595, parts (hereinafter called the works) to be plated are suspended by hangers movable horizontally over and along a succession of fixed processing tanks and are immersed in the processing tanks by lowering and raising the hangers. The works suspended by the hangers are transported by a dedicated transporting unit which moves along a pair of rails fixed to the ceiling, and the driving of which is controlled by a computer. Further, data about processing conditions, such as a processing time of the works and a current value, are read and stored by the computer; based on the data, the hangers are moved by the transporting unit over the processing tanks to perform the plating of a plurality of works simultaneously.
Japanese Patent Laid-Open Publication No. Sho 63-30399 discloses a transportation system for transporting works to each of successive processing tanks. In the transportation system, the works are transported by a carriage movable on a pair of rails fixed to the floor so that the carriage is movable between two series of processing tanks parallel to the rails. A hanger-manipulator arm mounted on the vehicle for suspending the works can position hangers over each processing tank series and is horizontally turnable and vertically movable to immerse the works in the processing tanks.
This plating line is exemplified by a nickel-plating line, a brass-plating line and a zinc-plating line; each kind of works common in plating type are plated in an individual shared plating line. In this conventional plating line, a multiplicity of processing tanks filled with the same kind of plating liquid are arranged in an effort to improve the manufacturing efficiency in mass production, and for this purpose, a plurality of various pre-processing tanks (electrolytic degreasing tank, weak-acid neutralizing tank, etc.) used.
According to the foregoing prior art, since the processing tanks of each step and their associated devices are arranged in the factory as a dedicated line, it is useful when manufacturing the same kind of products by a large quantity, but when manufacturing various kinds of products by a small quantity, many steps and facilities would be wasteful in flexible manufacturing, thus lowering the availability. Further, in recent years, plating lines are required to perform various plating processes demanded by customers quickly, and it is necessary to manufacture many kinds of products efficiently without adding any facility and hence increasing the cost of production.
As it depends on the variation of the number of works and the number of kinds of the works, availability of each plating line differs from one another. As a result, there would be an excess of processing tanks in a low-availability plating line, while there would be a shortage of processing tanks in a high-availability plating line. Yet if they increase the number of hangers or carriages was increased to solve such problem, a large scale of addition and reconstruction of facilities would have been inevitable and quick measures could not have been taken to cope with the added facilities.
Further, there are some plated works which require to be re-plated with the same or different kind of plate and sometimes it is necessary to provide another series of processing tanks for the re-plating. On such occasion, the works would not be plated in a single substantially continuous series of processing steps and they are transported between the first series of processing tanks to the second series of processing tanks for the re-plating manually.
In the above-mentioned plating, the plated works would be deteriorated, e.g. discolored, when they are left in wet for a long time; in order to cope with this problem, a drying step is added. Grease and dust would stick to the accumulated works due to the atmosphere in the factory, or a natural oxidized film would occur on the metal surface; in order to cope with this problem, facilities for performing electrolytic degreasing, washing, weak-acidic saturation, etc. are added. Therefore, although these added facilities are common facilities among the individual processing lines, under the influence of the availability of each processing line they belong to, they are not used efficiently. Accordingly, the cost of production and the space occupied by the facilities are increased, thus lowering the productivity. If the first and the second plating steps can be performed continuously, the drying step and the pre-processing step would be unnecessary.
Further, the same problems as those described above also exist in the process of surface-treatment, such as alumite-treatment and a predetermined process to be performed by immersing the works in some liquid.